We have demonstrated that the near-infrared system can successfully identify vulnerable plaques in aortic specimens from human autopsies. A company InfraReDx, has been formed to develop a catheter, light source, and detector system for clinical use. Because extensive preliminary data are available, we have chosen the Fast Track application. We have the following specific aims: 1. To perform infrared and histology correlations in human coronary artery tissue in approximately 150 specimens from 10 autopsy cases. 2. To develop a near-infrared catheter, light source and detection system for use in rabbits. 3. To utilize the system in a study of 20 cholesterol-fed rabbits to detect vulnerable aortic plaque. We anticipate that we will achieve sensitivity and specificities > 75% to identify plaques in the rabbit study, thus setting the stage for use in patients in Phase II of this application. PROPOSED COMMERCIAL APPLICATIONS: In addition to the identification of vulnerable plaque usage, the spectroscopy method is likely to be of benefit for multiple other diagnostic uses. These include diagnosis of tissue in the lungs, bladder, GI tract, and central nervous system. InfraReDx will develop these applications after the work for detection of vulnerable plaque is completed.